kernel: pass mutability on explicitly to new lists

src/tietze.c

@@ -1482,7 +1482,8 @@ static Obj FuncREDUCE_LETREP_WORDS_REW_SYS(Obj self, Obj tzrules, Obj a_w)
      }
      else {
         // make space for the new word
-        nw = NEW_PLIST(TNUM_OBJ(w),newlen);
+        nw = NEW_PLIST_WITH_MUTABILITY(IS_MUTABLE_OBJ(w), TNUM_OBJ(w),
+                                       newlen);
 
        // addresses
        wa=ADDR_OBJ(w);

src/vecffe.c

@@ -859,7 +859,7 @@ static Obj ZeroVecFFE(Obj vec)
                TNUM_OBJ(vec) <= T_PLIST_FFE + IMMUTABLE);
     len = LEN_PLIST(vec);
     assert(len);
-    res  = NEW_PLIST(TNUM_OBJ(vec), len);
+    res = NEW_PLIST_WITH_MUTABILITY(IS_MUTABLE_OBJ(vec), T_PLIST_FFE, len);
     SET_LEN_PLIST(res, len);
     z = ZERO_SAMEMUT(ELM_PLIST(vec, 1));
     for (i = 1; i <= len; i++)

src/vector.c

@@ -47,7 +47,8 @@ static Obj SumIntVector(Obj elmL, Obj vecR)
 
     // make the result list
     len = LEN_PLIST(vecR);
-    vecS = NEW_PLIST(TNUM_OBJ(vecR), len);
+    vecS = NEW_PLIST_WITH_MUTABILITY(IS_MUTABLE_OBJ(vecR), TNUM_OBJ(vecR),
+                                     len);
     SET_LEN_PLIST(vecS, len);
 
     // loop over the elements and add
@@ -93,7 +94,8 @@ static Obj SumVectorInt(Obj vecL, Obj elmR)
 
     // make the result list
     len = LEN_PLIST(vecL);
-    vecS = NEW_PLIST(TNUM_OBJ(vecL), len);
+    vecS = NEW_PLIST_WITH_MUTABILITY(IS_MUTABLE_OBJ(vecL), TNUM_OBJ(vecL),
+                                     len);
     SET_LEN_PLIST(vecS, len);
 
     // loop over the elements and add
@@ -253,7 +255,8 @@ static Obj DiffVectorInt(Obj vecL, Obj elmR)
 
     // make the result list
     len = LEN_PLIST(vecL);
-    vecD = NEW_PLIST(TNUM_OBJ(vecL), len);
+    vecD = NEW_PLIST_WITH_MUTABILITY(IS_MUTABLE_OBJ(vecL), TNUM_OBJ(vecL),
+                                     len);
     SET_LEN_PLIST(vecD, len);
 
     // loop over the elements and subtract

tst/testinstall/kbsemi.tst

@@ -77,5 +77,16 @@ gap> KnuthBendixRewritingSystem(N, \<);
 Knuth Bendix Rewriting System for Monoid( [ m1, m2 ] ) with rules 
 [ [ m2, m1 ] ]
 
+# the reduced word has the mutability of the given word
+gap> w := ReduceLetterRepWordsRewSys([ [ [ 1, 2 ], [ 3 ] ] ], [ 1, 2, 4 ]);;
+gap> w; IsMutable(w);
+[ 3, 4 ]
+true
+gap> w := MakeImmutable([ 1, 2, 4 ]);;
+gap> w := ReduceLetterRepWordsRewSys([ [ [ 1, 2 ], [ 3 ] ] ], w);;
+gap> w; IsMutable(w);
+[ 3, 4 ]
+false
+
 #
 gap> STOP_TEST("kbsemi.tst");

tst/testinstall/kernel/vecffe.tst

@@ -124,5 +124,15 @@ gap> SMALLEST_FIELD_VECFFE([Z(2), Z(4)]);
 gap> SMALLEST_FIELD_VECFFE([Z(8), Z(4)]);
 64
 
+#
+# ZeroSameMutability
+#
+gap> v := [ Z(5), 0*Z(5) ];; IS_VECFFE(v);
+true
+gap> IsMutable(ZeroSameMutability(v));
+true
+gap> IsMutable(ZeroSameMutability(MakeImmutable(v)));
+false
+
 #
 gap> STOP_TEST("kernel/vecffe.tst");

tst/testinstall/kernel/vector.tst

@@ -0,0 +1,30 @@
+#
+# Tests for functions defined in src/vector.c
+#
+#@local v, w
+gap> START_TEST("kernel/vector.tst");
+
+# sum and difference of a vector and a scalar have the mutability of the vector
+gap> v := [ 1, 2, 3 ];;
+gap> w := 1 + v;; w; IsMutable(w);
+[ 2, 3, 4 ]
+true
+gap> w := v + 1;; w; IsMutable(w);
+[ 2, 3, 4 ]
+true
+gap> w := v - 1;; w; IsMutable(w);
+[ 0, 1, 2 ]
+true
+gap> MakeImmutable(v);;
+gap> w := 1 + v;; w; IsMutable(w);
+[ 2, 3, 4 ]
+false
+gap> w := v + 1;; w; IsMutable(w);
+[ 2, 3, 4 ]
+false
+gap> w := v - 1;; w; IsMutable(w);
+[ 0, 1, 2 ]
+false
+
+#
+gap> STOP_TEST("kernel/vector.tst");